Where to go from here?

[Djaving]

I have a 68 c10 fleetside 2wd that just finished having hotchkis tvs suspension, seats from a 2014 silverado, moser rear end, wilwood 6 piston in front and 4 piston in the rear. Also, i had a 396 bbc rebuilt. My biggest weakness is the motor so i am looking for some ideas. At the end of the day i want a truck that i can drive in the summer as well as autocross every once and a while. After spending too much (still in pain from paying for all the work done already) i need some ideas to get more power without breaking the bank. My first thought was a 6.0l turbo but i am not educated about turbo motors. Please share your opinions. I would like around 550-600 hp to the wheels. You will find pics below! Also, this forum has been a great source of info so thank you.